The Mind-Body Problem is how a non-material mental substance can causally influence the material body. Ryle's 1949 book The Concept of Mind is regarded by many thinkers as having eliminated the immaterial mind and "dis-solved" the mind-body problem, which Ryle saw as the result of what he called a "category mistake."

In some ways influenced by Ludwig Wittgenstein, who thought many philosophical problems were caused by misuse of language, Ryle said the category mistake was applying properties to a non-material thing that are logically and grammatically appropriate only for a category including material things.

With his remarkable ability to turn a phrase, what Ryle even more famously did was to stigmatize "mind" as the "Ghost in the Machine." Unfortunately, the phrase greatly advanced the enlightenment idea of "Man a Machine." And it helped prepare the way for today's revolution in cognitive science based on the "computational theory of mind," with the digital computer the model for intellectual operations.

Not that Ryle himself thought of man as a mechanical system or machine. Far from it. Though he described both body and mind as a "field of causes and effects" and likened the motion of the planets to a "clockwork," he thought minds were "not bits of clockwork, they are bits of non-clockwork." (p.20)

Since biology established its title as a science, he says,

The Newtonian system is no longer the sole paradigm of natural science. Man need not be degraded to a machine by being denied to be a ghost in a machine. He might, after all, be a sort of animal, namely, a higher mammal. There has yet to be ventured the hazardous leap to the hypothesis that perhaps he is a man. (p.328)

For Ryle, free will was invented to answer "the question whether human beings deserve praise or blame." He conflates free will with moral responsibility, committing the ethical fallacy," assuming with Kant that our actions must be moral to be free.